The treatment of wastewater within large populated areas is typically performed by conveying wastewater through a network of pipes to a centralized located treatment facility where, most often, a mechanically supported aerobic biological process is used to treat the wastewater to specified levels of quality prior to being released back into the environment. These large public or privately managed treatment systems have ongoing staff and monitoring requirements to ensure that the treated wastewater can meet specified discharge requirements thereby protecting environmental and public health.
In rural areas, where piped conveyance networks are to costly or not feasible, wastewater is treated by an onsite sewerage system, which is typically a septic tank and subsurface dispersal system, that is managed by a private individual or the homeowner. The sewerage system involves conveying wastewater to a septic tank where the solids contained within the wastewater are allowed to separate into what are typically three semi distinct zones. The area between the upper scum zone and the bottom sludge zone is a zone containing a certain percentage of suspended solids, colloidal material and dissolved materials it is typically referred to as the clear zone. As wastewater enters the septic tank an equal portion leaves via an outlet positioned within the middle clear zone and is typically called effluent. The effluent is then discharged for the most part by gravity to a subsurface dispersal system that allows microorganisms within the soil to further treat the wastewater so that it will not constitute a health risk or cause environmental problems.
As population densities and water use within rural areas using septic systems have greatly increased the simple gravity type septic system is becoming challenged and often cannot provide effective wastewater treatment. To improve upon the quality of the effluent prior to being discharged, most typically into the subsurface soil environment, a number of aerobically supported wastewater treatment processes have been developed and are generally classified as aerobic treatment systems or units.
Aerobic treatment systems perform the conversion of the anaerobic effluent from the septic tank or other pre-treatment process with the introduction of air and thereby improving effluent quality prior to being discharged into soil or other receiving environments.
There exist today two principle aerobic supported processes; the first and most common process used is the activated sludge or suspended growth process, where microorganisms are freely suspended as agglomerated particles in an aerobically agitated and mixed environment. The second is the attached growth process or sometimes referred to as packed bed or fixed-film process wherein microorganisms are attached to the surfaces of solid inert material or media where they develop a biofilm.
The two principle processes as described above are often part of new treatment design requirements for providing greater then septic effluent quality discharges. However the vast majority of existing wastewater treatment systems are septic tank treatment systems and many are contributing to environmental and health risks.
A number of methods have been developed to address the possibility of converting an existing septic tank and to improve effluent quality. Representatives of such prior art examples are herein described with the following U.S. patents:
U.S. Pat. No. 5,162,083 Nov. 10, 1992 Forbes, where Forbes claims an apparatus for converting a standard anaerobic septic tank system into a highly efficient aerobic wastewater treatment system.
U.S. Pat. No. 6,554,996 Apr. 29, 2003 Rebori, where Rebori claims an apparatus for converting a typical anaerobic septic tank system into an efficient aerobic treatment system for treatment of liquor containing biodegradable wastes. The system includes a collapsible reactor module that can pass through a relatively small opening in the septic tank cover. The reactor module contains media through which the liquor to be treated can be recirculated and aerated.
U.S. Pat. No. 6,942,788 B1, Sep. 13, 2005 Cox where Cox claims a reactor chamber for placement in a wastewater treatment system. The reactor includes an air distribution manifold having a series of air release sites positioned below the fixed channel growth media and adapted to release air which disperses upwardly through the fixed channel growth media.
U.S. Pat. No. 7,252,766 B2 Aug. 7, 2007 Stuth, where Stuth claims a method and apparatus for treating wastewater wherein a submerged stand alone perforated cylinder reactor pod containing aerobic bacterial growth media and a draft tube with air pressure induced pumping action creates a spray or splash pattern so as to recirculate aerated liquor through the media and to the area surrounding the cylinder pod. Free interchange of mixed and unmixed liquor is provided via the perforation in the cylindrical pod wall.
These aerobic conversions are often very difficult to be installed with respect to the majority of existing septic tanks and can cause further problems by creating an agitated mixed liquid environment within the septic tank that increases the amount of suspended solids discharged from the tank and potentially compromises the effluent acceptance rate of the subsurface dispersal system.